Applicant's disclosure is directed to the selection and positioning of mobile-appliance location determining sensors in a wireless communication network. The disclosure assists in the pre-installation design of a mobile-appliance location determining system which utilizes a network infrastructure overlay location approach (as opposed to techniques where the location is determined with modifications to the mobile-appliance) where equipment is installed within the wireless network base stations and/or switching centers to determine the mobile-appliance location.
The use of wireless communication devices such as telephones, pagers, personal digital assistants, laptop computers, etc., hereinafter referred to collectively as “mobile-appliances”, has become prevalent in today's society. Recently, at the urging of public safety groups, the government has begun to require that the providers of mobile-appliance communication services geolocate, or determine the geographic position, of the mobile-appliance in certain circumstances. For example, the Federal Communication Commission (FCC) has issued a geolocation mandate for providers of cellular telephone communication services in order to geolocate a cellular telephone used to make a 911 emergency telephone call. An accuracy standard (FCC 94-102 E911) has been established by the FCC, which the geolocation systems must meet. Accordingly, the providers of cellular telephone services are interested in location determining systems which meet the accuracy standard at the minimum cost.
In addition to E911 emergency related issues, cellular telecommunications providers are developing location-enabled services for their subscribers including roadside assistance, turn-by-turn driving directions, concierge services, location-specific billing rates and location-specific advertising.
There are two major approaches to determining the location of a mobile-appliance. One approach is appliance based and requires modification to the conventional mobile-appliance so that the mobile-appliance is capable of determining its own location, e.g., through the use of GPS or some other location system. The other approach is network based and requires modifications to the communication network so that location sensors can determine the location of the mobile-appliance based on the communication signals transmitted between the mobile-appliance and the network. Applicant's disclosure is directed to the selection and placement of mobile-appliance location determining sensors through the network in order to locate a mobile-appliance.
There are presently a number of techniques available to locate mobile appliances. These include time difference of arrival (TDOA), angle of arrival (AOA), radio fingerprinting, reverse link power measurements, and collateral data matching (i.e., map or other features useful in estimating location). Each of these techniques has associated with it a theoretical and practical location accuracy, and an associated cost to implement. The techniques vary widely in their performance as a function of the radio frequency (RF) propagation environment, base station geometry and wireless air interface. For each of the techniques, there exists many implementation variants and permutations. For example, TDOA can be implemented using two or four RF channels to measure time of arrival, and can include spatial filtering techniques to enhance performance in certain RF environments. Each of these location capabilities has associated with it a different cost, with cost generally increasing for increased accuracy performance.
A conventional technique for deploying location determining sensors has been to co-locate the sensors with each of the base stations in a communication network in order to process the communication signals received at the base station. The location determining accuracy provided by such a deployment is then checked by randomly traveling to various geographic locations within the coverage area of the communication area with an independent location determining equipment, i.e., GPS, and comparing the independent location determination from GPS with the location determined from the location determining sensors at the base stations. If the location accuracy of the system is not sufficient, additional location determining sensors can be added apart from the base stations, or the sensors can be replaced with more capable sensors to improve the accuracy of the system. This method of installing and measuring the accuracy of the sensors is labor intensive and expensive.
Other employment techniques have positioned the location determining sensors at selected base stations and added additional sensors on an ad hoc basis as the accuracy verification using GPS or other independent means identified areas having substandard location determining accuracies.
Thus, the overall cost and performance of the location determining system is largely driven by the number of location determining sensors installed, as well as the types of sensors installed. It is for this reason that a detailed planning system and method is critical to design a location determining system for performance and cost effectiveness.
Accordingly, it is an object of the present disclosure to provide a novel system and method for determining the position of location determining sensors in a communication system.
It is another object of the present disclosure to provide a novel system and method for selecting location determining sensors having various capabilities in order to meet a predetermined accuracy standard at the least cost.
It is a further object of the present disclosure to provide a novel system and method of positioning location determining sensors based on estimated accuracies without the necessity of actually measuring communication signals.
It is yet another object of the present disclosure to provide a novel system and method of location determining sensors having various capabilities to address the varied signal propagation and site geometries in the communication coverage area.
It is still another object of the present disclosure to provide a novel system and method for modeling the transmit power of a mobile-appliance.
It is yet still another object of the present disclosure to provide a novel system and method of estimating the TDOA, AOA or collateral data matching error for a location determining system.
It is still another object of the present disclosure to provide a novel system and method of presenting the accuracy results of a location determining system as accuracy contour lines overlaid on a geographic map.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the disclosure pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.